59 ansi overvoltage protection on hydro generator 1

[uhpo]

I have a generator 10 MW, and the manufacturer specifications says voltage must be on +/- 5 % of Vn and ask me how i´ll avoid the generator works out of this area, i read IEEE standards and sugest for this point a ajustment of 110 % of Vn, and with this ajustment i think i didn´t protect generator as manufacturer claims..... for this what´s wrong manufacturer. the standard or there´s other way to protect the unit for working out of this area...
thanks.... cause i´m a little confused....

 

[waross]

If you use 110% when the manufacturer states 105%, the manufacturer may not honor the warranty in the event of a failure. I don't think that the IEEE standards will will honor a warranty claim either.

Bill
--------------------
"Why not the best?"
Jimmy Carter

 

[uhpo]

but the question is why the manufacturer claim for 5 % if standard said 10%?

 

[rbulsara]

Over voltage settings usually are associated with some time delay. Shorter time delay is required for higher OV. If the relay is smart enough you can have two levels of OV with different time delays.

By the way, standards are not laws. The mfr. may be taking a conservative approach. Try talking to some other engineer at the mfr. Only the mfr. can answer as why they say what they say.

Rafiq Bulsara

http://www.srengineersct.com

 

[uhpo]

but your opinion is to keep the value on 5%

 

[rbulsara]

I did not say that. I can't render my opinion without knowing much else about the project.

Rafiq Bulsara

http://www.srengineersct.com

 

[powerjunx]

agree, IEEE standards aren't laws; simply a standard that provides guides to practitioners. Some mfrs are conservative enough thus suggesting the 5% min recommended setting while 10% max'm operating limits, though it complies with the such standard, in this case warranty may void.


"..the more, the merrier" Genghis Khan

 

[burnt2x]

Whatever it is the OEM is afraid of (setting OV at +/-5%) can be answered by the OEM alone. You can set your protections any level you want but don't expect the OEM to cover your butt if the equipment gets busted. Most insurers are great at finding negligence or non-compliance to specified operating limits set by OEMs. You could squeeze more than what the OEM specified, (at your own risk) but don't expect they'd go easy on you, IMO. Sometimes, we want to experiment and to go over the limits but limits are limits! Beyond that point, your on your own.

 

[uhpo]

i think all or close to all generators today are manufactured on +/- 5 %, if this is true i still don´t undertand why IEEE didn´t change into 5%?

 

[uhpo]

thanks all for your time and response

 

[uhpo]

On nema MG 10-2001 (R2007)about squirrel motors states that voltage must be +/- 5 %, someone could tell me if there is on hydro units some kind of reference to the nominal voltage of the hydro generador, your help is really apreciated.
thanks

 

[wolf39]

Your company obviously has ordered a generator with a standard voltage variation of plus/minus 5%. Had you asked for plus/minus 10%, the OEM had designed the generator accordingly.

A generator with plus/minus 10% will be designed slightly more conservative as far as stator flux densities are concerned because core iron losses are higher when running at 10% overvoltage. Excitation current then is also higher, resulting in higher field temperatures. The groundwall insulation also would have been increased slightly had you asked for plus/minus 10% in the first place. Nevertheless, running at plus 10% should not really jeopardise your generator unless the OEM went to the limits with their design. Running at minus 10% would increase stator winding temperatures.

To overcome your problem I'd suggest you to adjust the transformer tap changer.

Wolf

http://www.hydropower-consult.com